Long-range sensor system, particularly for heavy torpedoes

ABSTRACT

A long-range sensor system, particularly for heavy torpedoes, comprising a group of high and medium frequency sensors (2) disposed on the forward part of the torpedo (1) and an additional group of low frequency sensors (3) distributed along the sides of the torpedo, thus increasing the useful range and acquisition capability with respect to the counteracquisition capability of the target ship.

DESCRIPTION

The present invention relates to a sensor system particularly for heavytorpedoes intended for long-range launching (over 30 km).

Historically torpedoes have always entrusted their forward part with therole of antenna for acquisition and tracking of the target (ship).

Given its size, the possible shapes of the forward part of the torpedo(flat, ogive or hemispherical) and the laying precision required of thesystem, the antenna frequencies currently employed are higher than 20KHz, which results in a somewhat modest acquisition range, of the orderof a few kilometers.

Consequently, torpedoes with the sensor systems currently in use cannotbe employed for long ranges (of the order of 30 km) in that the lowacquisition ranges do not make it possible to compensate for significanterrors in the position of the target at the time of launching.

On the other hand, it is not feasible to use very low frequency sensorsin the forward part of the torpedo since the antenna size would not besufficient for the directivity needed.

The solution currently adopted is to use, a group of high frequencysensors, with a range of about two-three kilometers, and a group ofmedium frequency sensors, with a range of about four-six kilometers, allin the forward part of the torpedo, an arrangement which presents thelimits mentioned above and is therefore subject to thecounteracquisition range of the target, which will be discussed below.

The aim of the invention is to overcome the above limits, making itpossible to match the increased acquisition capability of the launchplatforms to the requirements foreseen for modern weapon configurations.

The aim is achieved, according to the invention, by providing for afurther group of low-frequency sensors distributed along the sides ofthe torpedo, in addition to the high and medium frequency sensorsarranged in the forward part of the torpedo.

With such a sensor distribution, the system can operate in long-rangelaunch conditions, even if there is a significant error in the knowledgeof the target position when the launches are carried out.

In fact, the acquisition range of the low-frequency sensors distributedalong the sides of the weapon is considerably greater than that of thesensors in the forward part, and is certainly able to compensate for theuncertainties in the target position.

Moreover, by analyzing the ability of a ship to detect an attackingtorpedo and that of the torpedo to detect the target ship, i.e. thecounteracquisition and acquisition abilities, it is possible to adjustthe speed of the torpedo, so that it conducts the attack without thetarget being able to react with the necessary timeliness.

Further characteristics of the invention will emerge more clearly fromthe detailed description that follows, referring to a purely exemplaryand therefore non-limiting embodiment, illustrated in the attacheddrawings, in which:

FIG. 1 is a schematic side view of a torpedo with an ogive head,equipped with a sensor system according to the invention;

FIG. 2 is a schematic cross section showing the arrangement of theadditional lateral sensors according to the invention;

FIG. 3 is a schematic side view of the front part of a flat-headedtorpedo;

FIG. 4 is a diagram showing the areas covered by the various groups ofsensors disposed on the torpedo;

FIG. 5 is a diagram showing the variation in the acquisition capabilityof the torpedo and the counteracquisition capability of the ship withthe torpedo at different speeds and equipped with side antennas ofdifferent measurements.

FIG. 1 shows a heavy torpedo 1, intended for long-range launches (over30 km) provided with a sensor system according to the invention.

In particular, 2 indicates the area intended for the currently used highand medium frequency sensors, situated in the forward part of theweapon, whereas 3 indicates the additional area intended for thelow-frequency sensors distributed on the sides of the torpedo 1.

The situation is the same in FIG. 3, where the arrangement in area 2 ofthe high and medium frequency sensors 2 changes because of the differentshape of the torpedo head, in this case flat instead of ogive.

FIG. 4 schematically shows the areas covered by the various groups ofsensors, the currently used ones 2 in the forward part of the weapon andthe additional ones 3 according to the invention.

In this Figure A indicates the area covered by the traditional sensors 2at the high frequencies in use; B indicates the area covered by thetraditional sensors 2 operating at intermediate frequencies and C theadditional area covered by the low frequency sensors 3, according to theinvention, distributed on the sides of the weapon.

As can be seen from the diagram, the acquisition range foreseen for thearea C, about four-fold that of the area A, is certainly able tocompensate for uncertainties in the position of the target.

Therefore, with such a distribution of the sensors, the system canoperate under long-range launching conditions, even if the launches arecarried out with a significant error in the knowledge of the targetposition.

In other words, the low frequency sensors 3 distributed along the sidesof the torpedo make a rough long-distance location of the target, whileduring the approach phase the traditional high and medium frequencysensors 2 come into play.

Referring now to the diagram in FIG. 5, which shows the acquisitionranges of a torpedo equipped with the sensor system of the invention,with different antenna measurements, according to the speed, and theacquisition ranges of a ship travelling at two different speeds, theoptimal speed conditions in which the weapon can conduct an attackwithout the target being able to react with the necessary timeliness canbe calculated.

More specifically, the diagram in FIG. 5 shows the torpedo speed inknots on the abscissa and the acquisition ranges on the ordinate both ofthe torpedo and the target ship.

In the diagram the curves marked with solid squares and empty squares,solid rhombi and empty rhombi refer to torpedoes equipped with sideantennas whose surface in meters is indicated to the right of thediagram, while the curves marked a solid triangle and an empty trianglerefer to a ship travelling at a speed of 15 knots and 25 knots,respectively.

From this diagram, analyzing the ability of a ship to detect anattacking torpedo and that of the torpedo to detect the target ship, itcan be seen that for certain pairs of ship/torpedo speeds, theacquisition by the attacking torpedo is greater than thecounteracquisition capability of the ship, whereas for other pairs ofship/torpedo speeds the situation is reversed.

In particular, it can be seen that the acquisition capability of thetorpedo is greater than the counteracquisition capability of the ship inthe areas of the diagram lying to the left or above the curves marked bytriangles, while in the other area of the diagram the counteracquisitioncapability of the ship prevails.

Clearly, to determine the condition of greatest success of the launch,the optimal situation is that in which the weapon can develop its attackat the best speed in which its acquisition powers exceed those ofcounteracquisition, that is in the area of the diagram above the curvecorresponding to the ship's performance.

To provide a practical example, if the ship proceeds at 15 knots (curvemarked by solid triangles) and the torpedo has a side antenna two meterlong (curve marked by empty squares), the torpedo can advance at themaximum speed of 40 knots shown on the diagram up to a distance of about8.5 km. From the ship, then it has to reduce its speed, for example to35 knots, to prevent the counteracquisition range of the target shipfrom prevailing. The speed of 35 knots can be maintained up to adistance of about 6 km from the target ship, then it must be reduced,for example to 30 knots, a situation in which the acquisition power ofthe torpedo remains superior to the counteracquisition power of theship.

From what has been described it is obvious that a torpedo equipped withthe sensor system of the invention, as illustrated in FIGS. 1, 2 and 3,can reach considerable ranges, in any case considerably greater than anypresent counteracquisition range.

This characteristic can be exploited by the weapon to conduct the attackadjusting its own speed so that the counteracquisition range of the shipis always shorter than the current distance, as shown in the examplecited above. A "surprise" effect is thus achieved, allowing the weaponto penetrate the potential defence lines of the countermeasures beforethese can be alerted.

Moreover, as already stated, even in long-distance launch conditions theweapon can attain acquisition conditions in the presence of considerablyerrors in the knowledge of the target position. This considerablyincreases the launches' chances of success.

What is claimed is:
 1. A sensor system, particularly for heavytorpedoes, comprising a group of high and medium frequency sensors (2)positioned in the forward part of the torpedo, and a group of lateralsensors (3), characterized in that said sensors (3) are low-frequencypassive sensors and are positioned along the sides of the torpedo with alongitudinal extension, functioning as a directive receiving antenna,along longitudinal planes of the torpedo.
 2. A sensor system accordingto claim 1, characterized in that said heavy torpedoes (1) are aimed forlong range launches, until beyond 30 Km, said directive low frequencyantenna made of the lateral sensors (3) being apt for detecting theapproximately coming direction of the noise signals emitted by thetarget on the long distances, said high and medium frequency sensors (2)positioned in the forward portion of the torpedo, coming into operationat near distances in order to precisely locate the target.
 3. A sensorsystem according claim 1, characterized in that an adjustment of thetorpedo speed is foreseen, so that the counteracquisition range of thetarget ship is always inferior to the current distance.